Fuel supply apparatus for internal combustion engine



July 7, 1964 F. w. LINK 3,139,875

FUEL SUPPLY APPARATUS FOR INTERNAL COMBUSTION ENGINE Filed Aug. 22, 1961 3 Sheets-Sheet 1 INVENTOR.

BY fled [Jilin/,

F. W. LINK July 7, 1964 FUEL SUPPLY APPARATUS FOR INTERNAL COMBUSTION ENGINE 3 Sheets-Sheet 2 Filed Aug. 22, 1961 IMPROVED LOW SPEED TORQUE CURVE INVENTOR. Fred ZZ/ZL'n/f/ July 7, 1964 F. w. LINK 3,139,875

FUEL SUPPLY APPARATUS FOR INTERNAL COMBUSTION ENGINE Filed Aug. 22, 1961 5 Sheets-Sheet 5 $9 47 48 35 7 7631 118 119 72 14? a2 f zj Q1 103 4 -j a? .2 5 9446366 F 4? 48 49 77 76 36 42 72 73147 51 5 1 4 g1 g2 g4 Q3 51 k g {58M v (5 6366 INV EN TOR.

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United States Patent 3,139,875 FUEL SUPPLY APPARATUS FOR INTERNAL COMBUSTION ENGINE Fred W. Link, Columbus, Ind, assignor to Cnmmins Engine Company, Inc, Columbus, Ind., a corporation of Indiana Filed Aug. 22, 1961, Ser. No. 133,132 14 Claims. (Cl. 123-140) This invention relates generally to a fuel supply apparatus for an internal combustion engine, and more particularly to a fuel supply apparatus for a multi-cylinder engine of the diesel type.

It is a general object of the invention to provide a novel fuel supply apparatus for delivering accurately metered quantities of fuel to the respective cylinders of an internal combustion engine under varying load and speed conditions.

A more particular object is to provide a novel fuel supply apparatus of the foregoing character, which is adapted to increase the torque of the engine during the low-speed operating range thereof, thereby providing greater acceleration and power output throughout this range.

Another object is to provide a novel fuel supply apparatus of the foregoing character which is adapted to provide an immediate reduction in the torque of the engine when the latter reaches a predetermined maximum speed.

These and other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a vertical sectional view of a fuel supply unit embodying the features of the present invention and adapted for use with a fuel supply apparatus of the aforementioned character;

FIG. 2 is a vertical sectional view taken along the line 22 of FIG. 1;

FIGS. 3 to 5, inclusive, are a series of fragmentary sectional views of a portion of the fuel supply unit of FIG. 1 and showing the positions of the parts thereof under varying operating conditions; and

FIG. 6 is a torque versus engine speed curve of a diesel engine utilizing a fuel supply apparatus incorporating the features of the present invention, and illustrating in dotted line the increased low-speed torque characteristics .of the engine in relation to the full line normal torque in many respects to that disclosed in the Neville M.

Reiners copending application entitled, Fuel Supply Apparatus for an Internal Combustion Engine, Serial No. 72,440, filed November 29, 1960, in that the primary purpose of both systems is to deliver accurately metered quantities of fuel to the respective cylinders of a dieseltype internal combustion engine under varying load and speed conditions. Both systems effect the foregoing by controlling the pressure of the fuel supplied to the injectors of the engine, such control being achieved throughout the normal operating speed range of the engine by means of an engine-driven centrifugal control mechanism which is effective to variably discharge, as a function of the speed of the engine, a portion of the fuel from the conduit means which supplies the fuel to the injectors. Such mechanism also functions as a governor when the engine is operating at idle and maximum speed.

The present apparatus, while employing a fuel supply unit incorporating the aforementioned engine-driven centrifugal control mechanism as a means for obtaining a precise control of the quantity of fuel supplied to the injectors, differs therefrom in that the present control mechanism includes means adapted to increase the torque of the engine throughout the low speed range thereof, as

well as means for immediately reducing the torque of the engine when the latter reaches or exceeds a predetermined maximum speed. Such increase in torque is achieved by superimposing an additional control on the fuel discharging means, which is effective to decrease the amount of fuel discharged throughout the low speed range of the engine. An increase in the fuel pressure supplied to the injectors is thereby obtained and consequently the torque of the engine is increased. The torque reduction feature, at maximum speed, is achieved by cutting off the supply of fuel to the injectors and at the same time connecting the fuel supply passages extending to the injectors to a Zone of low pressure.

The fuel supply unit of the present invention is adapted for use with a fuel supply apparatus such as is disclosed and claimed in the aforementioned Reiners application. Because the various features of the present invention are embodied in the fuel supply unit of such an apparatus, only that portion of the apparatus will be described in detail hereinafter. However, in order to facilitate an understanding of the present invention, a brief description of such a fuel supply apparatus will be included.

A fuel supply apparatus for which the present fuel supply unit is adapted generally comprises a fuel reservoir or tank from which fuel is drawn by a pump connected by a series of lines to a fuel supply unit, such as the fuel supply unit 10 of the present invention, illustrated in FIGS. 1 and 2. The fuel supply unit 10 supplies fuel at a controlled pressure to supply passages in the fuel injectors of the engine. Metered quantities of fuel from the supply passages of the injectors are injected into the cylinders of the engine. The quantity of fuel injected is a function of the speed of the engine and the pressure of the fuel supplied to the injectors. Excess amounts of fuel are returned to the tank through return passages in the injectors and connected return lines. The supply lines thus comprise conduit means connecting the source of fuel under pressure, or pump, with the fuel delivery means or injectors.

As shown in FIGS. 1 and 2, the fuel supply unit 10 comprises a housing 11 in which various components are mounted. Fuel is drawn into the unit 10 by a pump 12 mounted on the side of the housing 11 and connected to the fuel tank. In the present instance, the pump 12 is mounted in its own housing 13 and is of the positive displacement gear type having a driven gear 14 which meshes with a drive gear 16. The drive gear 16 is mounted on a shaft 17 which extends into the housing 11. The inner or left end, indicated at 18, of the shaft 16 is splined to a coupling 19 which is driven by a stub shaft 21 connected by a fitting 22 to the crankshaft of the engine. The pump 12 is thus driven by the engine. In order to eliminate pressure peaks or pulsations in the fiow of fuel leaving the pump 12, a pulsation damper 23 may be provided. The damper 23 is connected to the high pressure or discharge side of the pump 12 by a fitting 24.

Fuel from the discharge side of the pump 12 flows through a passage 26 (FIG. 1) in the housing 11 to a fuel strainer 27, which is preferably of the combined magnetic and filter screen type. A removable cap 23 provides access to the strainer 27. Upon leaving the strainer 27, the fuel flows through a series of interconnected passages in the housing 11 to the lower portion 29 (FIG. 2) of a vertical bore 31 in the housing 11. The lower portion 29 of the bore 31 is separated from the upper portion, indicated at 32, by a plug 33. The lower end of the portion 29 intersects a horizontal bore 34 which is connected at its inner end to an engine-driven centrifugal control mechanism indicated generally at 40. The mechanism 41] is adapted to divide the fuel flow from the passage 34 into two branches, one branch comprising a main or primary fuel path for supplying fuel to the engine throughout the normal operating speed range of the engine including speeds above idle and up to maximum, and the other branch comprising an idle fuel flow path for supplying fuel to the engine during starting and idle.

To this end, the mechanism generally comprises a tubular barrel 41 (FIGS. 1 and 2) which is mounted in a bore 42 in the lower part of the housing 11. A tubular sleeve 43 is mounted in the barrel 41, and a movable member in the form of a plunger 44 is rotatable and axially shiftable in the bore of the sleeve 43. An engine-driven centrifugal device, indicated generally at 45, is located at the left end of the plunger 44, as shown in FIG. 1, and tends to shift the plunger 44 to the right with a force which varies as a function of the speed of the engine. A spring-pack 46 is located at the right end of the plunger 44- and tends to oppose the force of the device 45.

Fuel in the passage 34 flowing toward the control mechanism 4t) enters a space provided by a flattened portion 47 (FIGS. 2 and 3) on the adjacent side of the barrel 41. Extending radially inwardly through the barrel 41 from the flattened portion 47 is a port 48. A second radially inwardly extending port 49 is formed in the sleeve 43, in registry with the port 48. The ports 48 and 49 are disposed toward the right end of the barrel 4-1 and sleeve 43 as viewed in FIGS. 3 to 5, inclusive. The plunger 44 includes a portion 51 of reduced diameter adapted to be moved into registry with the port 49 at cranking speeds and remaining in registry throughout the entire operating speed range of the engine up to maximum speed. It will thus be apparent that the entire fuel flow from the pump 12 passes through the ports 48 and 49, and around the reduced portion 51, as will be described more fully hereinafter.

In order to complete the main fuel flow path through the control mechanism 46, another port 52 (FIGS. 2 and 3 to 5, inclusive) is formed in the sleeve 43 on the opposite side of the plunger 44 and in general transverse alignment with the port 49, the port 52 being of lesser axial width than the port 49. A registering horizontally extending port 53 is formed in the barrel 41 in alignment with the port 52, the port 53 being connected to another vertical bore 54 (FIG. 2) in the housing 11. The bore 54 extends upwardly in the housing 54 to a manually controlled throttle 55 which intersects the bore 54. The throttle 55 has a transverse passage 56 therethrough, through which the fuel flow passes. The bore 54 extends beyond the throttle 55 and is intersected at its upper end by a horizontal bore 57. The bore 57 communicates with the upper portion 32 of the bore 31 by means of a short diagonal passage 58. From the upper portion 32, fuel flows through a shut-off valve 59 and thence by the supply lines to the injectors of the engine.

In order to control the pressure of the fuel in the main flow path or branch to the injectors throughout the normal operating speed range of the engine, the control device 46 includes means for discharging or by-passing a portion of the fuel from the flow through the main branch. To this end, a duct 63 is formed in and extends longitudinally of the plunger 44. The duct or bore 63 communicates at its inner end with the reduced diameter portion 51 by a pair of transverse holes 64 and extends to and opens at 65 at the right-hand end of the plunger 44 as viewed in FIGS. 1 and 3 to 5. Cooperating with the open end 65 of the plunger 44 is a closure 66 in the form of a cup having its end wall adapted to abut against the open end 65 of the plunger 44.

The closure 66 constitutes part of the spring-pack 46 and is effective to control the by-pass or discharge flow of fuel through the duct 63 in accordance with the opposing forces exerted by the spring-pack 46 and the centrifugal device 45 on the plunger 44 and the pressure of the fuel in the duct 63. The pressure of the fuel in the duct 63 will, when sufficiently high, separate the closure 66 from the open end 65 of the plunger 44 to permit fuel to discharge therethrough. Fuel that has been discharged or by-passed through the duct 63 is directed back to the intake side of the pump 12 through a series of connected passages, indicated at 67, 68 and 69 in FIG. 1. Axial movement of the plunger 44 is effected by the centrifugal device 45. The centrifugal device 45 thus comprises a carrier 78 having a pair of pivotally mounted weights 71 secured thereto. The carrier 78 includes a tubular shaft 72 rotatably journaled in a flanged bearing 73 mounted in a cover portion 74 for the housing 11. The shaft 72 includes a flange 76 providing a thrust washer between the carrier 78 and the end face of a gear 77 mounted on the shaft 72. The gear 77 meshes with a larger gear 78 mounted on and driven by the stub shaft 21.

The weights 71 include a pair of laterally offset arms 79 which engage a thrust washer 81 secured to the outer or left end of the plunger 44 by a T-shaped keying member 82. The laterally extending portion, indicated at 83, of the member 82 is flat so that the arms 79 may lie on either side of the portion 83. The axially extending portion, indicated at 84, of the member 82 is cylindrical and extends into a bore 86 in the end of the plunger 44. A transverse pin 87 secures the member 82 and thrust washer 81 to the plunger 44. Rotation of the weight carrier 70 thus causes rotation of the plunger 44 due to the overlapping arrangement of the arms 79 with the member 82. Pivotal movement of the weights 71 is transmitted through the arms 79 to the thrust washer 81 to thus effect axial movement of the plunger 44.

An auxiliary spring assembly 88 comprising a tubular sleeve 89 of a predetermined axial length and a coil spring 99 of a predetermined length and rating is also mounted on the left end of the plunger 44, one end of the sleeve 89 and spring 90 engaging the thrust washer 81. The spring 99, when operable upon engagement with the end face of the sleeve 43, serves to reduce the force of the weights 71 on the plunger 44 throughout the intermediate to maximum speed range of the engine, and the sleeve 89, when moved into engagement with sleeve 43, serves to limit the amount of movement of the plunger 44 toward the right. The length of the spring 90 determines the torque peak of the engine and the rating of the spring 90 determines the amount of torque.

As heretofore mentioned, the mechanism 40 is adapted to discharge or by-pass a portion of the fuel flow from the pump 12 through the duct 63 to control the pressure of the fuel supplied to the injectors, the pressure of the fuel in the duct 63 acting against the closure 66 and tending to separate it from the end 65 of the plunger 44. The spring-pack 46 opposes such separation of the closure 66 as well as movement of the plunger 44 toward the right due to the force exerted by the weights 71.

The spring-pack 46, in this instance, includes the cupshaped closure 66 and means for urging the closure 66 toward the open end 65 of the duct 63. Such means comprises a pair of springs 91 and 92 which bear against the closure 66 and are operative during the idle speed range of the engine. The spring 91 engages the closure 66 at its internal end Wall and the spring 92 engages the annular end face of the closure 66. For urging the closure toward the left at speeds above idle and in order to provide a seat for the opposite ends of the springs 91 and 92, the spring-pack 46 includes a cup-shaped guide member 93 and a heavier spring 94. The closure 66 is slidably mounted in the guide member 93, and the latter is provided with an internal shoulder 96 which acts as a stop for the closure 66 (FIGS. 4 and 5) when springs 91 and 92 are fully compressed as when the engine is operating at speeds above idle. The closure 66 is provided with a plurality of longitudinal grooves 97 which prevent any piston effect.

The guide member 93 and spring 94 are slidably mounted in a tubular member 98 carried by the housing 11. The tubular member is enclosed by a housing 99 removably secured to the side of the housing 11. The guide member 93 is held in abutting engagement with the end of the barrel 41 (FIGS. 1 and 3) by the spring 94 at idle speeds, but is unseated at speeds above idle when the closure 66 abuts the shoulder 96 under the increasing force exerted by the centrifugal device 45 and the pressure of the fuel in the duct 63. Thus, at idle speeds, the springs 91 and 92 provide the by-pass control force of the spring-pack 46, and at speeds above idle, the heavier spring 94 provides this force. The discharged or by-passed fuel flowing out of the open end 65 of the plunger 44 is returned to the intake side of the pump 12 mainly through the connected passages 67, 68 and 69.

From the foregoing, it will be evident that the pressure of the fuel at the injectors is controlled by the mechanism 40, such pressure being controlled by the amount of fuel by-passed or discharged through the duct 63. The amount of fuel by-passed also depends upon the speed of the engine due to the fact that variations in engine speed are translated into a varying force by the centrifugal mechanism 45 which force is opposed by the force of the spring-pack 46.

The centrifugal control device 40 is also adapted to control the flow of fuel through the idle flow path when the engine is operating at idle speed. Thus, during idling,

the mechanism 40 is adapted to control fuel flow to the and 112, respectively. The ports 111 and 112 extend radially upwardly through the sleeve 43 and barrel 41, as indicated in FIGS. 1 and 2. In FIGS. 3 to 5, inclusive, the ports 111 and 112 have been shown as extending downwardly in order to simplify their illustration. A short passage 113 (FIGS. 1 and 2) registers at its lower end with the port 112 and at its upper end with a bore 116 in the housing 11 in which the throttle 55 is mounted. Fuel from the passage 113 passes through a diagonal idle passage 117 in the throttle 55, which unites with the transverse passage 56 on the downstream side of the throttle 55. From there, the fuel flows through the bore 54 in the housing 11 to the injectors of the engine. The ports 111 and 112, passages 113 and 117, thus constitute the idle branch of the fuel passage.

At idle speed, the force of the centrifugal device 45 acting on the plunger 44 is sufficient to shift the latter toward the right to the position illustrated in FIG. 3. In this position, the reduced portion 51 registers with the idle port 111 and partially with the main outlet port 52 in the sleeve 43. Because of the fact that the throttle 55 normally will have been moved to a position substantially closing the passage 56 prior to starting, the flow through the main flow branch, which includes the ports '52 and 53, is minor.

As previously, mentioned, the output of the pump 12 exceeds the needs of the injectors at idle speed, and consequently a portion of the fuel flowing around the reduced portion 51 will be by-passed through the holes 54 and duct 63 in the plunger 44 back to the inlet side of the pump. Thus, the primary control of the pressure of the fuel at idle speed is achieved by the by-pass flow through the 'duct 63.

If the engine speed should tend to exceed the idle speed,

the mechanism 40 becomes effective to exert a governor control of the idle flow through the port 111 to prevent the engine from exceeding such speed. Thus, as the engine tends to exceed idle speed, the plunger 44 is shifted of the spring 147 bears.

ernor action to restrict the fuel flow through the idle branch.

As heretofore mentioned, at idle speed and up to maximum speed, control of the fuel flow in the main branch of the mechanism 40 is primarily obtained by controlling the amount of fuel bypassed through the duct 63. As will be apparent from FIG. 4, when the engine is operating at speeds above idle, the shoulder 118 has closed the idle port 111, but does not move across the main outlet port 52 until speeds approaching maximum are reached. Thus, throughout the normal operating range of the engine, the mechanism 40 is effective to control the pressure of the fuel in the main flow branch by controlling the amount of fuel by-passed through the duct 63. During such normal operating speed range, the heavier spring 94 of the spring-pack is operative, and throughout the intermediate to maximum speed range, the spring of the auxiliary spring assembly 88 becomes operable to modify the force output of the centrifugal device 45. In addition to the foregoing by-pass control of the fuel supplied to the injectors of the engine in the normal operating range, the fuel supply unit 40 includes a control compensating for changes in the temperature of the fuel which would otherwise effect the quantity of fuel supplied to the injectors due to corresponding changes in the viscosity of the fuel. Such other control is embodied in the throttle 55, and is fully described in the copending Reiners application.

Where the fuel supply unit 10 is to be used in conjunction with an engine in an automotive application, it is desirable that the engine develop a fairly high torque throughout its low speed range in order to provide rapid acceleration of the vehicle. To this end, the fuel supply unit 10 of the present invention includes means cooperating with the mechanism 40 for increasing the pressure of the fuel supplied to the engine in its low speed range. Such means, in this instance, adds a force to that exerted by the centrifugal means 45 and comprises an auxiliary plunger 146 and spring 147 mounted in the tubular shaft 72 driving the Weight carrier 70, the shaft 72 being counter-bored as at 148 to receive the plunger 146 and to provide a shoulder 149 against which the outer end The plunger 146 includes a pair of rod-like extensions 151 and 152 extending axially from the respective ends thereof. The extension 151 extends from the right or inner end of the plunger 146 toward the governor plunger 44, and the extension 152 extends from the left end of the plunger 146 between the coils of the spring 147. The plunger 146 and its extension 151, together with the spring 147, have an overall axial length such as to cause the extension 151 to engage the member 82 on the governor plunger 44 and compress or preload the spring 147 when the engine is stopped. When the engine is operating at idle speed, the force of the spring 147 is thus added to the force developed by the governor weights 71 tending to urge the plunger 44 toward the right. The resisting force exerted by the spring-pack 46 is correspondingly increased and thus a higher fuel pressure is required to separate the plunger 44 and the closure 66. Consequently, the presincreased pressure results in an increased quantity of fuel supplied to the injectors so that a greater torque is developed by the engine throughout its low speed range. The effect of spring means 146, 147 on the torque curve of the engine throughout the low speed range thereof is indicated by a .dotted line for the torque curve illustrated in FIG. 6,

As the governor plunger 44 begins to move to the right with increasing engine speed, a progressively lesser force will be exerted by the spring 147. At some intermediate speed, such as about 1000 rpm. (FIG. 6), the spring 147 will be completely extended and will not exert any further force on the end of plunger 44. The torque curve 7 in FIG. 6. FIG. 4 illustrates the position of the parts of the mechanism 40 when the engine is operating in its normal operating range, the auxiliary plunger 146 and spring 147 having ceased to function.

The provision of the plunger 146 and spring 147 not only increases the idle torque of the engine and thus the acceleration capabilities of the engine from idle to intermediate speeds, but also provides increased fuel during cranking and starting. The force of the spring 147 is such that, during cranking and starting, no by-pass flow through the duct 63 occurs. Consequently, substantially the entire output of the pump 12 is applied to the injectors.

In addition to providing means for increasing the torque of the engine throughout the low speed range thereof, the present invention also includes means for rapidly reducing the pressure of the fuel in the supply passages of the unit when the engine reaches a predetermined maximum speed. Such reduction in fuel pressure will, of course, cause an immediate reduction in the torque of the engine and, in addition, the engine becomes effective for use as a brake when the torque has been reduced. Such pressure reducing means in this instance is effective to cut off the supply of fuel to the engine and to relieve the pressure of the fuel in the injectors and the lines leading thereto. To cut off the supply of fuel, the shoulder 118 moves across and closes the port 52 when the engine reaches a predetermined maximum speed, as illustrated in FIG. 5. To reduce the pressure of the fuel, a second reduced portion 156 on the plunger 44, is provided, which is disposed between the reduced portion 51 and the end of the plunger 44 engaged by the centrifugal means 45. The portion 156 is of sufiicient length to extend beyond the end of the barrel 41 and sleeve 43 for all positions of tie plunger, so that the reduced portion 156 communicates with the interior of the housing 11 which constitutes a zone of low pressure. The portion 156 also defines a shoulder 157 at its inner or right end, which is axially spaced from the shoulder 118 by a distance substantially equal to the spacing between the main and idle fuel outlet ports 52. and 111, respectively. Thus, when the plunger 44 moves to the right a sufiicient distance, the shoulder 118 moves to substantially close the main outlet port 52 and the shoulder 157 moves to open the idle outlet port 111, as illustrated in FIG. 5.

Even though the main fuel branch or passage to the injectors is closed by the shoulder 118 when the engine reaches or exceeds a predetermined maximum speed, the fuel in the supply passages and conduits to the injectors is at a high pressure at this time, and a significant amount of fuel would be injected into the cylinders when an overspeed condition develops. The provision of the second reduced portion 156 eliminates this condition by establishing a connection between the supply passages and lines with the low pressure zone, namely, the interior of the housing 11. Because the idle passage 117 in the throttle 55 interconnects with the main flow passage 56 in the throttle (FIG. 2) for all rotative positions of the throttle, the passages extending to the injectors are thus connected to a low pressure zone, namely, the interior of the housing 11, and the pressure of the fuel at the injectors will immediately be reduced. Since the sleeve member 89 is in engagement with the end of sleeve 43 at maximum speed, notches or grooves 158 are provided in the adjacent end face of the sleeve member 90.

It will thus be apparent that the fuel supply apparatus of the present invention provides improved operating characteristics for an engine with which it is used in that an increased low speed torque output of the engine is achieved, which permits more rapid acceleration of the engine, and as a result of the maximum speed fuel shutolf and venting of the fuel passages and supply lines to the injectors, the torque output of the engine is immediately reduced at such maximum speed.

I claim:

1. A fuel supply apparatus for a multi-cylinder internal combustion engine, including a source of fuel under pressure, delivery means for supplying fuel to the respective cylinders of the engine, conduit means connecting said source and said delivery means for supplying fuel to the latter, and means for controlling the pressure of the fuel at said delivery means comprising speed responsive means for variably discharging fuel from said conduit means upstream from said delivery means, and means for modifying such discharge only during lowspeed operation of the engine for varying the pressure of the fuel at said delivery means and thereby varying the torque of the engine during such low-speed operation.

2. A fuel supply apparatus according to claim 1, in which said modifying means is effective to reduce the amount of fuel discharged by said fuel discharging means to thereby increase the pressure of the fuel at said delivery means during low-speed operation of the engine to increase the torque thereof.

3. A fuel supply apparatus for a multi-cylinder internal combustion engine, including a source of fuel under pressure, delivery means for supplying fuel to the respective cylinders of the engine, conduit means connecting said source and said delivery means for supplying fuel to the latter, and means for controlling the pressure of the fuel at said delivery means comprising a movable member defining a discharge duct communicating with said conduit means for discharging fuel therefrom, a closure for said duct, spring means for urging said closure toward duct closing relation with said duct, means responsive to the speed of the engine exerting a force urging said movable member toward duct closing relation with said closure, the pressure of the fuel in said duct tending to oppose said spring means and said speed responsive means, and means coacting with said speed responsive means for adding to the force exerted by the latter on said movable member during low-speed operation of the engine, thereby to increase the pressure of the fuel at said delivery means during low-speed operation of the engine to increase the torque thereof.

4. A fuel supply apparatus according to claim 3, in which said speed-responsive means comprises centrifugal means acting on one end of said movable member to urge the latter toward duct closing relation, and said torque increasing means comprises another spring means acting on said movable member to increase the force exerted on said movable member during low-speed operation of the engine.

5. A fuel supply apparatus according to claim 4, in which said other spring means acts on the same end of said movable member as said centrifugal means and exerts a progressively decreasing force on said movable member with increasing engine speed throughout the low speed range of the engine, whereby the torque developed by said engine is increased throughout said low speed range and the rate of increase is less with increasing engine speed throughout said range.

6. A fuel supply apparatus for a multi-cylinder internal combustion engine, including a source of fuel under pressure, delivery means for supplying fuel to the respective cylinders of the engine, conduit means connecting said source and said delivery means for supplying fuel to the latter, mechanism for controlling the pressure of the fuel at said delivery means comprising a housing having a passage forming part of said conduit means, a plunger slidably mounted in said housing and having a duct therethrough communicating at one end with said passage and open at one end of the plunger for discharging fuel from said conduit means, a closure for said open end, enginedriven centrifugal means for urging the plunger toward said closure for varying the effective size of said duct, spring means opposing said centrifugal means and acting on said closure tending to urge the latter toward said plunger, and second spring means acting on said plunger for urging the latter toward said closure throughout the low operating speed range of the engine, said second spring means being effective to increase the force urging said plunger'toward said closure, whereby the effective size of said duct and the amount of fuel discharged is reduced throughout said low-speed range and the torque of the engine is increased throughout said range.

7. A fuel supply apparatus according to claim 6, in which said second spring means includes a second plunger engageable with the other end of said first-mentioned plunger, and a spring for urging said second plunger into engagement with said first-mentioned plunger.

8. A fuel supply apparatus according to claim 7, in which said spring exerts its greatest force on said second plunger during the starting and idle speed range of said engine, and a lessening force on said plunger becoming zero as the engine reaches an intermediate speed.

9. A fuel supply apparatus according to claim 8, in which said centrifugal means is located at one end of said plunger, said closure and said spring means are located at the other end of said plunger, and said second spring means is located at the same end of said plunger as said centrifugal means.

10. A fuel supply apparatus according to claim 9, in which said centrifugal means includes a drive shaft aligned with the first-mentioned plunger, and said second plunger and its associated spring are mounted in said drive shaft.

11. A fuel supply apparatus for a multi-cylinder internal combustion engine, comprising a source of fuel under pressure, delivery means for supplying fuel to the respec tive cylinders of the engine, conduit means connecting said source and said delivery means for supplying fuel to the latter, control mechanism for controlling the pressure of fuel in said conduit means, said conduit means including a pair of branch passages in said control mechanism and extending downstream therefrom and connected together upstream from said delivery means, one of said branch passages being connected to supply fuel to said delivery means during the idle speed range of the engine and the other of said branch passages being connected to supply the main fuel flow to said delivery means throughout the operating range of the engine, said control mechanism including means for shutting off the flow of fuel to said delivery means through said other branch passage at maximum engine speed and to discharge fuel from said idle speed branch passage to reduce the pressure of the fuel at said delivery means and thereby reduce the torque of the engine when the latter reaches maximum speed.

12. A fuel supply apparatus according to claim 11, in which said control mechanism includes a plunger intersecting said branch passages and having a first reduced portion defining a shoulder movable relative to said branch passages for controlling fuel flow therethrough during the idle and operating ranges of the engine and for shutting off the flow of fuel through said operating range branch passage to said delivery means at maximum engine speed, said plunger having a second reduced portion communicating with said idle speed branch passage to discharge fuel therefrom for reducing the pressure at said delivery means when said shoulder shuts off the fuel flow through said operating range branch passage when said engine reaches said maximum speed.

13. A fuel supply apparatus according to claim 12, including a housing having a bore with said plunger slidably mounted in said bore, said housing having said branch passages therein intersecting said plunger bore, said bore at one end communicating with a Zone of low pressure in said housing, and said second reduced portion being effective to connect said idle speed branch passage to said low-pressure zone when said shoulder on said plunger shuts off fuel flow to said delivery means at maximum speed.

14. A fuel supply apparatus according to claim 11, including a throttle connecting said branch passages.

References Cited in the file of this patent UNITED STATES PATENTS 2,670,725 Cummins Mar. 2, 1954 2,727,503 Reiners Dec. 20, 1955 2,833,218 Evans May 6, 1958 2,937,637 Heiser May 24, 1960 

1. A FUEL SUPPLY APPARATUS FOR A MULTI-CYLINDER INTERNAL COMBUSTION ENGINE, INCLUDING A SOURCE OF FUEL UNDER PRESSURE, DELIVERY MEANS FOR SUPPLYING FUEL TO THE RESPECTIVE CYLINDERS OF THE ENGINE, CONDUIT MEANS CONNECTING SAID SOURCE AND SAID DELIVERY MEANS FOR SUPPLYING FUEL TO THE LATTER, AND MEANS FOR CONTROLLING THE PRESSURE OF THE FUEL AT SAID DELIVERY MEANS COMPRISING SPEED RESPONSIVE MEANS FOR VARIABLY DISCHARGING FUEL FROM SAID CONDUIT MEANS UPSTREAM FROM SAID DELIVERY MEANS, AND MEANS FOR MODIFYING SUCH DISCHARGE ONLY DURING LOW- 